Composite key by @IdClass

Question

hello, discuss the style of composite key by @IdClass. take the Category as example. this class use the name and createDate as comp. key. the entity part looks like:
*@Entity*
*@IdClass(CategoryPK.class)*
*public class Category {*
public Category() {}
*@Id*
protected String name;
*@Id*
protected Date createDate;
*public String getName(){.............}*
*public Date getCreateDate(){..............}*
*public void setName(){.............}*
*public void setCreateDate(){.........}*
but somebody add the @Id on getter method like:
*@Entity*
*@IdClass(CategoryPK.class)*
*public class Category {*
public Category() {}
protected String name;
protected Date createDate;
*@Id*
*public String getName(){return this.name}*
*@Id*
*public Date getCreateDate(){return this.createDate}*
*public void setName(){.............}*
*public void setCreateDate(){.........}*
it seem like both work after trying. but i have referred to at least three books, all of them just mention the first style. one of book even emphasize we must add the @id on the properties. so i am confused what's the different between them, and why the second style is not mentioned?
Thanks

Answer 1

I think for the real ORM expertise in Oracle, try the TopLink/JPA forum here on OTN.
-steve-